Extension rule



May 30, 1939- F. o. CARLSON 2,160,304

EXTENSION RULE Filed Nov. e, i957 Patented May 30, 1939 EXTENSION RULE.

Frederick O. Carlson, New York, N. Y., assigner to Master Rule Manufacturing Company, Inc., New York, N. Y., a corporation of New York Application November 6, 1937,A Serial No. 173,135

4 Claims.

This invention relates to improvements in ex-` tension rules and particularly with relation to the jointmembers by means of which the individual rule sections are secured together lso as to permit relative longitudinal or sliding movement.

An important object of this invention involves the construction of the joint members and the manner in which they are attached to the rule sections so as to increase the usefulness of the l0,I rule and eliminate a present large ,source` of `4 J breakage resulting from constructions now com monly employed. A further object of the invention is the proy connecting the rule sections in suchmanner that under excessive abuse or strain the rule sections may separate without breaking or-destroying them so that they may be readily reassembledby the user at no cost to him -and without necessitating their return to the manufacturer for repair. Y

A more specific object of thev invention is to provide joint members of this type which have a spring or snap action in holding them attached to the rule sections.

Another specic object of the invention is the provision of a combination in an. extension rule of a plurality of wooden rule sections Ainterconnected by joint members which have at least one portion which has a spring or snap association with one of each pair of associated rule sections whereby under undue strain they may become separated without breakage of the wooden rule sections.

Other and more speciilc objects will be apparent from the following detailed description when taken in connection with the attached drawing.

This invention resides substantially in the combination, construction, arrangement and relative location of parts, all in accordance with the following disclosure.

In the accompanying drawing,

Figure l is a side elevational view of an eX- 45 tension rule constructed in accordance with this invention showing one section partly extended.

Figure 2 is an enlarged detailed view of two adjacent sections with their connecting joint members. f

Figure 3 is a cross-sectional view taken on the line 3 3 of Figure 2.

The extension rule illustrated in the drawing is of the type commonly known and employed extensively in the industries at the present time. It comprises, as illustrated, a plurality of wooden yvision in extension rules of joint members interl rule sections l, which are generally rectangular l .in cross-section and all of which are of uniform length. Thus when all of the sections are completely retracted the rule forms a substantially regular rectangle. Each sectionl is provided along each side. edge with a groove running throughout the length thereof `which may be of any desired cross-sectional form, as for example rectangular, as illustrated. The two terminal sections at their free terminalends are provided in accordance with common practice'with metal protectingA tips2 which areA preferably made of spring or tempered brass. and attached thereto by reason of their resiliencyand .an adhesive, if desired.. Y

The remaining endsof `the terminal sections and both ends of .all of the other sections, are provided with the joint members which are directly concerned with'the subjectmatter ofthis invention. These joint members comprise, generally speaking, a pair cf-oppositely facing channels formed from a single piece of spring or tempered brass or other suitable material. As illustrated in the drawing., one of the channels comprises' a bottom wall l Ywhich-lies under. the rule section attheendfand 'a pairof side walls or flaps 5 which lie alongv the adjacent sides of the rule sections. The other channel section has. a base wall whichis an extension of the `wall 4, and a pair of downwardly projecting side walls 1,

the free edges Bof which are inturned at right angles to lie inthe grooves 43.v As .is quitecommon in this art, these joints have in addition to the construction illustrated and described, additional features of construction with which we are not here concerned, such as ears or tabs for positioning them on the rule sections and various forms of catches for holding the extensions in fully closed and open position.

The feature of this invention consists in the manner in which the side walls 5 are attached to the rule sections. It may be noted that it is common practice at the present time to strike out all these side walls and turn inwardly small ears which are bent over the adjacent side of the groove 3. This tab or ear may be thus llocked around one of the sides of the groove forming an interlocked connection therewith. A very common result of this construction is that when the rule is unduly strained or abused, that is to the extent that the rule section pulls out of the joint member, the side wall of the groove is broken oif because of the strong interlocking connection resulting from the inturned tab. This necessitates returning the rule to the manufacturer, making it unavailable for use to the owner, and necessitating an undesirable expense to him. Indeed the only way that the rule may then be repaired is to substitute for the broken section an entirely new one. Quite frequently the joint member is also damaged requiring its replacement. Since the cost of repair relative to the total original cost of the rule must be kept low, this` type of Work is a source of annoyanceand loss to the manufacturer who cannot readily charge the full lvalue of the service rendered. y

This problem has been solved by means of the construction herein employed wherein, as clearly illustrated in Figure 3, the. side. Walls 5- are bent` or crimped as indicated ati 6, in-to thegrooves 3 at the ends of the side walls or, where a stronger joint is required, throughouttheir length,I to formv a resilient inner lock which is adequate for all normal purposes. Theresulting rule isa reasonably strong structure adapted to all of the normal requirements thereof. The clamping action is aided by reason of the factthat an inherent resilientmaterial is used to fabricate the joint members. Y y

However, because ofL the construction employed, when the rule is actually strained,` or is abused, the woodA sections may separate from the joint members by reason of; the fact, that the crimped in portions 6 mayY slide over the adjacentv side walls o fthe-grooves-without breaking or destroying them'. Thus this type of joint protects the rule sections and adds the highly desirable featurethat strains and abuse may be relieved in` a manner that does not permanently injurethe ruler. The Owner. ofthe. fiile may himselfjquickly and readily repair itiiv simply forcing. the sepelatedV Seeiianbaelsinio the associatedioint .mem- 11er aridioriis. the sidewaiisbals into. plasmas for exemple by means ofabluntchisehihe. end ofthe, Screwdriver, and, the like. The resultthat Sucharepeir. may beniede ,immediately and the rule puthaglsiriteuse withqutanv expense to the owner.

From, the. aber/e description. it will, be. apnar.-

@ntie theseslsilled. in iheartthat the. snnie.tiire bi'.V means of. whichl the-objects (if this invention areatiainedmarbevaried by those skiiiesiinihe art without departure. fremihe noyeiscopeor the invention, herein. disclosed .,I, do not, therefore, desire to. be Strict1,y .1imited, to.v the. disclosurev as given fort purppses of. iliustratiombut ratherl to the scope of` the. claims1v granted me.

vsubstantially rectangular rule lengths having grooves along the sides thereof and a plurality of joint members for vinterconnecting the adjacent ends of associated pairs, said joint members each comprising a channel having its side walls folded into the grooves of Aone section of one pair and A planar portions having V-shaped indentations releasably gripping the other section of the pair in the grooves. f y f 3. An extension' rule comprising a plurality lof substantially rectangularj rule `lengths having grooves along the s idesthereof, and a plurality of jointr members for interconnecting th'e adiacent endsV of associatedv pairseach joint member being made of a single piece of resilient metal and formed into a pair of oppositely facing channels, the side wallsnof one 'channel being folded around into the grooves of onesection of each pair and providing interlocking, sliding engagement therewith, and the side walls of the other channel being depressedpirlto th'egrooves ofthe4 other section of thepair toV releasably clamp it therein. y

4, An extension rule comprising a plurality of substantially rectangular rule lengths having grooves along the'sides 'thereoiand a plurality of joint membersv for interconnecting the adjacent ends of associatedlpairs, each joint member being made of a single piece 'of resilient metal and formed into apair oivoppositelyfacing channels, thesidewalls of on'e channel being folded around into the groovesof onesection of each' pair and providing p'ositive,'sliding engagement therewith, and the side walls of`the other channels lying againsttheside edgesl offtheother sectionvof the pair and having portions depressed into the grooves thereof, so asto resiliently and releasably hold the section therein.

` 'FREDERICK o. CARLSON. 

